The U.N. and a U.S. advocacy group warned that the detention of three senior southern Sudanese politicians during a crackdown Monday on pro-reform protesters in Khartoum could undermine the country's upcoming elections and its fragile north-south peace deal.
Police fired tear gas and used batons to break up a rally in the Sudanese capital that saw thousands calling for reforms ahead of April's presidential and national elections.
Authorities had banned the gathering and deployed security and military troops in and around the suburb of Omdurman ahead of the event.
The protest was organized by the main southern Sudan's People Liberation Movement, and several northern opposition parties. They called on President Omar al-Bashir's ruling northern party to amend laws necessary to ensure free and fair elections.
Following the violence in Khartoum, angry residents in the southern town of Wau set fire to an office belonging to the ruling northern party, according to Yambio Joel, who said he saw the torching from his office window.
The U.N. representative to Sudan, Ashraf Qazi, expressed concern over the violence and said it comes at a "very critical" stage in Sudan. "These developments could have adverse implications" on the north-south deal, he said.
The 2010 elections are a key component of the 2005 peace deal which ended more than 20-years of civil war between the north and south. The peace deal established a semiautonomous south and called for national and presidential elections.
The vote is also expected to pave the way for a referendum the following year in which the south would chose whether to secede from the north.
Two million people died in the civil war, which devastated the country's oil-rich south. The north-south conflict is separate from the war in the western Darfur region, which has killed more than 300,000 people over the past six years.
Pagan Amum, the secretary-general of the main southern Sudanese party, was among the three southern politicians detained. They were released after several hours.
"It is clear now there are no freedoms in Sudan. There is no way to organize free and fair elections," Amum said after his release.
John Prendergast, head of a Sudan program at the Washington-based Center for American Progress, said the U.S. should reconsider financial assistance to the Sudanese elections.
"Today's reaction by the ... security services demonstrates further that the U.S. should not be financing this electoral charade unless the laws are amended to allow the basics of a credible election," Prendergast said.
The president of south Sudan, Silva Kiir, called the detentions unjustifiable. He vowed to "use all the necessary means to ensure the country does not reverse to war."
London-based Amnesty International also condemned the Khartoum crackdown, saying it was an example of the "culture of violence" adopted by al-Bashir's government.
Mistrust between north and south runs deep. Southern officials complain the government in Khartoum is reneging on its obligations under the peace deal and is withholding revenues from the oil fields, many of them in the south.
Southern lawmakers have boycotted parliament sessions in Khartoum, complaining that al-Bashir's party is dragging its feet when it comes to amending laws that protect human rights and ensure freedom of expression.